The actual organization is launching an unprecedented publicity campaign, called "Operation Lemonade," to combat the negative image created by the book.

The movie adaptation of "The Da Vinci Code" is set to be released May 17. The plot contends that Jesus married Mary Magdalene and had descendants, and it claims that Opus Dei and the Catholic Church were at the center of a cover-up.

"Good Morning America" got an exclusive behind-the-scenes tour of Opus Dei's New York headquarters, and looked at the facts and fiction surrounding the group.

What Is Opus Dei's Mission?

Positive Interpretation: An innovative teaching on the sanctifying value of work, complete fidelity to the Catholic Church, and enabling each Catholic layperson to take full responsibility for the mission of sanctifying society.

Negative Interpretation: Often been accused of secrecy, ultraconservative beliefs, a right-wing political agenda -- dating back to Spanish dictator Francisco Franco in Spain -- and even cultlike methods.

The 'Da Vinci Code' Villain: Silas

In "The Da Vinci Code," Silas is a crazed albino monk who physically punishes himself and murders people in the name of his religion. Opus Dei, however, says the real Silas is peaceful and soft-spoken Silas Agbim, a stockbroker from Nigeria who lives in Brooklyn, N.Y., with his wife and has been a member of the group for 28 years.

"I'm not, of course, I'm not deep undercover," he said. "I am not an albino. I am not a monk -- far from that."

There are approximately 87,000 members worldwide; 3,000 in the United States

The organization was founded on Oct. 2, 1928, in Madrid, Spain, by St. Josemaria Escriva de Balaguer

It's believed to be worth $2.8 billion

The New York City headquarters cost $69 million, according to the Opus Dei communications office -- $61 million for the building itself; $8 million for furnishings

John Paul II was supportive of the organization and designated it a "personal prelature" -- meaning the prelate's jurisdiction is not linked to a territory but over persons wherever they be

Key Terms

From Time magazine

Associates -- Members who follow the most rigorous spiritual practices of Opus Dei life (including celibacy) but do not live in residence or retreat centers.

Cilice -- A spiked chain that some members strap around their upper thigh for two hours a day as an act of penance.

Cooperators -- Nonmembers who support the group through prayer, volunteer work or financial contributions.

Discipline -- A small, cordlike whip that some members use once a week to flagellate themselves during the recitation of a prayer.

The Norms -- Spiritual obligations that all members perform daily, including attending Mass, praying silently for 30 minutes twice a day, and reciting the Rosary and other prayers, usually after supper.

Numeraries -- The most committed members, who take vows of celibacy, live in Opus Dei centers, and practice corporal self-punishment.